1. Field of the Invention
This invention relates to the separation of greases and oils from wastewater using automatic processes and apparatus.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
Many industrial processes involve the generation of wastewater which is a mixture or an emulsion of oil or grease and water. In particular, services and wash areas for trucks and automobiles, heavy equipment, fork lifts, and engine rebuilders of ten generate wastewater from cleaning processes which combine oil and grease and water. In addition, process water used in asphalt plants, with compressors and generators, and in other industrial plants often use water for cooling. Such process water often becomes contaminated with oil and grease which leaks from the equipment. Finally, maintenance of a clean environment requires the removal of oil and grease from parking lot run-off, contaminated groundwater, holding ponds, and the washdown from oil and gasoline spills. All these and other processes generate wastewater which is a mixture or emulsion of oil or grease and water and which must be separated into the component fractions oil or grease and water. Grease, oil, fats, and other materials found in wastewater which have a density less than that of water will be referred to collectively in this application as "oil or grease" or as "oil". Water contaminated with oil or grease will be referred to collectively as "wastewater". Such wastewater cannot simply be released to the environment because of contamination to the rivers and estuaries which are the ultimate recipients of such waters.
There is a problem with the disposal of such wastewater in sewers because of the tendency of grease to coagulate on the internal walls of pipes and plug the lumen of the pipes, a particular problem at bends and valves. In addition, many jurisdictions charge a fee for the disposal of wastes having a high biological oxygen demand, such as wastewater, or may forbid its disposal in a municipal sewage system because of toxicity associated with the oil or grease which disrupts the sewage plant operation. Finally, the salvage value of oil or grease recovered from wastewater provides an additional economic incentive for separation and recovery of the oil and grease.
Grease separators generally include a tank in which the wastewater stream is allowed to stand while the grease and oil separate. The grease and oil accumulate at the top of the tank because grease and oil is less dense than is water. Conventional systems have electrical pumps and fluid level sensors which are used to transfer the wastewater stream or oil stream from one chamber to another. Such pumps inevitable create a mechanical emulsion of grease or oil and water which is difficult to separate and tends to confound the purpose of a grease separator. In addition, the use of electric pumps with a grease or oil separator carries an unavoidable element of fire hazard.
The present invention is free of pumps thereby avoiding pump-caused emulsion formation and avoiding any hazard of fire associated with electrical pumps and sensors.
U.S. Pat. No. 2,284,737 utilizes a continuous flow process to separate liquids of different specific gravities. The localized rates of flow and the direction of the flow of the incoming waste water are controlled to provide a constant body of water in the separator receptacle. This system uses a single chamber which is partially sectored with baffles.
U.S. Pat. No. 4,246,112 discloses an oil-water separator which stores and allows both the oil phase and the water phase to be reused.
U.S. Pat. No. 4,246,113 discloses an oil-water separator which contains two compartments. The separator is designed to restrict the flow of water from the first compartment into the second compartment which increases the residence time of the oil-water in the first compartment and thereby increases the separation of oil therein.
U.S. Pat. No. 4,268,396 discloses an oil recovery apparatus used for removing grease and/or oil from dish water and showing a preferred means for straining debris from the influent flow of contaminated water.
U.S. Pat. No. 5,178,754 discloses an apparatus for reducing the solids and oil/grease components of a water mixture. It includes devices for separating solids from liquids in a flow of solids and liquids and for separating oil/grease from water in a flow of oil/grease and water.
The present invention is advantageous over those in the prior art in that it is multichambered yet free of electrical pumps and sensors. This provides superior separation of oils and grease from wastewater by avoiding the generation of mechanical emulsions of oil or grease and water, which confound the purpose of the separator. In addition, the present invention avoids the fire hazard associated with electrical pumps and sensors.